Collecting email headers can be done the same way for OWA as well as Outlook on both Windows and Mac. The easiest method is to compose a new email and then drag the email whose headers you would like to collect into this new email. The message will be added as an attachment and all of its information, including headers, will be available to the support staff you are asked to send them to. Although this is the easiest way, users who are concerned about sharing message content may prefer an alternative which shares only header information.